This functionality has been in OpenSolaris for quite some time now. It really rocks hard. Make a safe quick rollback in seconds. Awesome. I can really understand why Fedora wants that functionality.

There's also experimental support in FreeBSD for the Boot Environment auto-snapshot feature for OS upgrades. Before an OS upgrade, a new BE is created, and you get a menu at boot that lets you select which BE to use. To "rollback", just boot into the previous BE and delete the erroneous one.

And if one puts /var and /usr/local onto ZFS filesystems, one can manually snapshot /var and /usr/local before installing/upgrading apps. If something goes wrong, just rollback to the previous snapshot and try again. (Technically, you'd want to put /var/db/pkg onto a separate ZFS filesystem as that is what gets updated during a port/package install, and not all of /var.) It's not automatic, but it's possible.